Surface Tension: is a force resulting from cohesiveness, which lowers to a minimum the number of molecules on the surface of a liquid. This creates a kind of invisible envelope which occupies the smallest possible surface. The surface tension represents the force of the film on the liquid surface. When one applies this principle to a minerals suspension, one can observe that the surface tension of water creates on the surface a layer which contains the finest particles of the suspension. This layer is very thin and created spontaneously.

Application to an isolated drop of the suspension: A drop is a volume of insulated liquid whose cohesion is ensured by the forces of surface tension. In the absence of external influence, the drops have a spherical form. Thus if one applies this reasoning to a drop of this suspension, the finest particles come to cover the surface of this one and leave in the centre a mass of a suspension richer in large particles.